Mars Polar Lander Mission Status

December 3, 1999
5 a.m. PST

Mars Polar Lander flight controllers opted to perform the last trajectory
adjustment of the mission early this morning, sending commands to the
spacecraft that will result in a short engine firing to target the
spacecraft to the desired landing site near layered terrain in the red
planet's south polar region.

Mars Polar Lander is scheduled to land on Mars shortly after noon Pacific
time on Friday, December 3. The first signal is expected to be received at
12:39 p.m. The entry, descent, and landing sequence is the most complex and
risky part of the mission.

The engine firing will take place at 5:39 a.m. Pacific time for 8 seconds,
said flight operations manager Dr. Sam Thurman. "This maneuver will
increase the entry flight path angle by 0.25 degrees, moving the flight
path from our most recent estimate, 12 hours prior to entry, of minus 13
degrees back to the target value of minus 13.25 degrees," Thurman said.
"We decided to perform the maneuver in order to ensure that the entry
flight path achieved will be very close to the planned trajectory. It puts
is just about right on top of the target point, which is in an area chosen
because the terrain provides for a safe touchdown."

During descent, the spacecraft will enter the Martian atmosphere traveling
at 6.9 kilometers per second (15,400 miles per hour). Onboard
accelerometers will sense when friction from the atmosphere causes the
lander to slow. From that time, it will be approximately 5 minutes and 30
seconds until touchdown on the surface, during which time the spacecraft
will experience G forces up to 12 times Earth's gravity and the temperature
of the heat shield's exterior will rise to 1,650 C (3,000 degrees F).

The Deep Space 2 microprobes, which are piggybacking on the lander, will be
jettisoned to the planet about 5 minutes before the lander enters the
Martian atmosphere. They will impact the Martian surface about 60
kilometers (about 30 miles) away from spot where Mars Polar Lander will set
down.

Mars Polar Lander is part of a series of missions in a long-term program
of Mars exploration managed by JPL for NASA's Office of Space Science,
Washington, D.C. JPL's industrial partner is Lockheed Martin Astronautics,
Denver. JPL is a division of the California Institute of Technology in
Pasadena.